The overarching goal of this project is to elucidate the molecular mechanism governing the catalysis and regulation of histone modification enzymes. We will use our Chaperone-Enabled Biology and Structure (CEBS) technology platform to study an important, but challenging group of epigenetic regulating enzymes. The lysine-specific histone methyltransferases (HMT) and their complementary partners, lysine demethylases (KDM) function as key mediators of epigenetic signaling through their actions as writers and erasers of post-translational modifications on histone proteins. Numerous recent studies have highlighted the importance of lysine methylation of histones leading to direct impact on DNA replication, repair, recombination, gene silencing, imprinting and RNA processes making these enzymes potential key targets for drug development. However, progress in gaining fundamental knowledge about structure-function relationships governing their modes of operation has been slow because they are multidomain proteins and have been recalcitrant to both structural and functional analyses. To overcome the existing barriers, we will generate specialized reagents called synthetic affinity binders or sABs that will be used as chaperones for crystallization, as well as customized affinity reagents for cell biologically applications. To accomplish our objectives we have assembled a world-class team of investigators that will exploit sAB reagents for both structure determination and high level biological assays. A major emphasis of our approach is to identify and structurally/biochemically characterize the molecular complexes in which the HMTs and KDMs function by using sABs that stabilize and enhance crystallization of the complexes. Thus, CEBS effort will rely on close ties to the large high throughput centers for protein production and structure determination of individual enzymes in multiple conformational states, enzyme-substrate complexes and multiprotein complexes. A unique strength of our approach is that we will provide crystallization chaperones and the information on interaction partners to the high throughput centers to greatly increase the probability of success of structure determination.